Field of the Invention
The invention relates to an optical lens, and particularly relates to an optical lens assembly.
Description of Related Art
In recent years, as use of portable electronic devices (e.g., mobile phones and digital cameras) becomes ubiquitous, techniques related to producing image modules have also been developed significantly, wherein the image module mainly includes an optical lens assembly, a module holder unit and a sensor, and the demand for minimized image module increases due to the compact and slim design of mobile phones and digital cameras. Moreover, as dimensions of a charged coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) are reduced and significant progress is made in related technology, the length of optical lens assembly in the image module is correspondingly reduced. However, in order to avoid reduction in optical performance and quality, good optical properties should also be achieved while the length of optical lens assembly is shortened. Image quality and image volume are two of the most important characteristics for an optical lens assembly.
The specification of portable electronic products (such as cell phone, cameras, tablet PC, personal digital assistant, photographic device used in car, etc.) is ever-changing, and the key components, i.e. optical lens assembly, is also developed diversely, which is not only applied to image-taking and recording, but is also applied to telephotography, moreover, along with the advance of image sensing technology, consumers' demand for image quality also increases. The size of the conventional micro telephoto lens is over 50 millimeters and the f-number is up to 4 or more, so as to be obviously unable to meet the specification of the existing portable electronic products. Accordingly, not only does the design of the optical lens assembly used in telephotography need to meet the requirement for good image quality and small lens space but also improvement of aperture stop size should also be taken into consideration.
However, it is not possible to accomplish the design of optical lens assembly having good image quality and micro-size by simply scaling down a lens having good image quality, and the design process involves consideration about material characteristics and further involves consideration about producing, practical issues on the production line such as assembly yield, design applied to the camera module, so the technical difficulties in producing of the micro-sized lens is much higher than those of the conventional lens.
Therefore, how to produce an optical lens assembly that meets requirements of consumer electronic products and has an improved image quality is always a goal in the industry and academy.